Its largely depends on what value BA has this aircraft insured for.......
Market value is naff all, but airline hull all risks insurance is on an agreed value basis, they could have it insured near to market vslue say $15-20m or they could have it insured at a much higher value, many leased aircraft would be insured at $50m.
Knowing BA own all these aircraft, it is likely they insure them at just above the net book value of the aircraft. BA assume a life of between 20and 25years for an aircraft, thus this aircraft is likely to have a value to BA not much higher than the cost of the last check.
Thus they will be discussing very carefully the options for this aircraft with their insurers.